diff --git a/src/bitmap.c b/src/bitmap.c
index a222539..d50e7d6 100644
--- a/src/bitmap.c
+++ b/src/bitmap.c
@@ -55,9 +55,9 @@ simdb_bitmap_compare(const unsigned char *a,
 }
 
 size_t
-simdb_bitmap_diffmap(unsigned char *diff,
-                     const unsigned char *a,
-                     const unsigned char *b)
+simdb_bitmap_diffmap(const unsigned char *a,
+                     const unsigned char *b,
+                     unsigned char *diff)
 {
   size_t i = 0;
 
diff --git a/src/bitmap.h b/src/bitmap.h
index eddf01b..b44ba06 100644
--- a/src/bitmap.h
+++ b/src/bitmap.h
@@ -29,15 +29,15 @@ simdb_bitmap_compare(const unsigned char *a,
 
 /**
  * @brief Make difference map of to bitmaps
- * @param diff Storage for difference map
  * @param a    First bitmap to compare
  * @param b    Second bitmap to compare
+ * @param diff Storage for difference map
  * @returns Size of generated map (now is @a BITMAP_SIZE)
  */
 size_t
-simdb_bitmap_diffmap(unsigned char *diff,
-                     const unsigned char *a,
-                     const unsigned char *b);
+simdb_bitmap_diffmap(const unsigned char *a,
+                     const unsigned char *b,
+                     unsigned char *diff);
 
 
 /**
diff --git a/src/simdb-query.c b/src/simdb-query.c
index 977953c..fea796f 100644
--- a/src/simdb-query.c
+++ b/src/simdb-query.c
@@ -162,7 +162,7 @@ int rec_diff(simdb_t *db, uint64_t a, uint64_t b, unsigned short int showmap)
   memcpy(two, &rec.data[REC_OFF_BM], SIMDB_BITMAP_SIZE);
 
   if (showmap) {
-    simdb_bitmap_diffmap(map, one, two);
+    simdb_bitmap_diffmap(one, two, map);
     simdb_bitmap_print(map);
     return 0;
   }